When designing a new tile installation, don't just think in terms of individual tiles. Instead think of whole surface and of adjacent surfaces, textures, and colors.
You do not have to rely heavily on decorative tiles to be decorative. If you want to use specially designed tiles, you have to make sure that they are integrated with the overall scheme. Often you can buy pleasing to the eye tiles to match the colors and sizes of manufacturer's regular tiles.
You can also decide to use a few hand painted tiles but you have to make sure that the sizes and the colors of the tiles are compatible. If you are planning to customize your tiles, be sure to discuss the colors and function of your total project with an artist or designer.